1. Field Of The Invention
The present invention relates to a magnetic head. More particularly, the invention relates to a magnetic head for large capacity, high transfer rate recording apparatus.
2. Description Of The Related Art
There is an increasing demand for large capacity, high transfer rate recording apparatus, for both image and data storage. Increased capacity requires narrow recording tracks and high linear recording densities. In order to increase linear density, the use of high-coercivity media, like metal particle or metal evaporated, is needed. In turn, higher saturation magnetization is needed in the record head material. High transfer rates demand faster relative head to tape speeds coupled with higher recording frequencies. High recording frequencies put additional demands on the head material.
Monolithic ferrite heads have been used in both magnetic disks and tape drives where they perform well when the coercivity of the recording media is less than 700 oersteds (Oe) and the highest frequency is 10 megahertz (MHz). However, due to the need for improved saturation magnetization and high frequency response, ferrite is not a good choice for newer applications. A so-called metal-in-gap (MIG) head can perform well on high coercivity media but suffers from the same limited frequency response as ferrite heads since ferrite is still the main part of the head core.
Layered metal (composite) and thin film heads, on the other hand, can be built with high saturation magnetization material and can function well at high frequencies. Historically, NiFe thin films have been the magnetic material of choice in a thin film head. However, NiFe has a low resistivity, 20 microohm-cm, and has poor wear resistance. FeSiAl (Sendust) alloys and amorphous materials have higher resistivities and better wear resistance.
Composite heads have been under development for some time and have been especially of interest for use in high definition television (HDTV) recorders. Most of the HDTV heads that have been reported in literature show adequate frequency performance of no greater than about 100 MHz.